package 
{
	import flash.display.Sprite;
	
	public class Ball extends Sprite
	{
		public var radius:Number;
		public var color:uint;
		public var vx:Number = 0;
		public var vy:Number = 0;
		public var mass:Number = 1;//质量
		public function Ball(radius:Number=40, color:uint=0xff0000,alpha:Number=1)
		{
			this.radius = radius;
			this.color = color;
			this.alpha=alpha;
			init();
		}
		public function init():void
		{
			graphics.beginFill(color,alpha);
			graphics.drawCircle(0, 0, radius);
			graphics.endFill();
		}
	}
}